Good Reasons.

From the perspective of the older generations (at least the ones young enough to have to work with them, boomers and GenX), there was a fairly sharp contrast in attitudes and work ethic.

Previous generations always had some of that going on, typically reflected in dress and music, but when they got into the workplace they came round pretty quickly.

Millennials, due to having *very* significant differences in upbringing did not come around to the old ways and that created long-standing friction. Those differences (technology and some trends in the education system and child-rearing concepts) created a sharp and significant generational divide.

While the M's have obviously had to somehow adapt to adulting and earning a living, there's still some lingering friction. Maybe just bad blood?

Yes, it was the "fault" of the booomers for screwing it up, but in fairness they simply didn't know. They didn't grasp the significance of tech/internet and they thought the new education and child-rearing ideas were actually better. Not the fault of GenX, I was in my twenties and focused on beer and tail, anything to do with kids was the furthest thing from my mind.

We finally seem to be getting around to banning phones in school, and maybe at all times for kids below a certain age.